Obama said Saturday that he preferred multilateral action but added, "It is not in the national security interest of the United States to ignore clear violations of these kinds of international norms."
The U.N. charter generally doesn't allow countries to attack other nations unless in self-defense or with approval from the U.N. Security Council. The Syrian government asked Ban "to shoulder his responsibilities for preventing any aggression on Syria," the state-run Syrian Arab News Agency reported.
Under U.S. law, Obama doesn't have to get Congress' approval to launch military action. The 1973 War Powers Resolution authorizes a president to initiate an attack as long as he notifies Congress within 48 hours. But internationally, a U.S. strike against Syria could be deemed illegal.
Any call for the Security Council to endorse action against Syria would face a sure veto from Russia and China, both Syria's allies. Chinese foreign affairs spokesman Hong Lei said Monday that Beijing is "gravely concerned that some country may take unilateral military actions."
"We believe that any action taken by the international community should abide by the purposes and principles of the U.N. charter ... so as to avoid complicating the Syrian issue and bringing more disasters to the Middle East region," Hong said.
And Russian Foreign Minister Sergey Lavrov said Moscow is "absolutely" not convinced by the evidence the Americans, British and French have shared so far.
"There are no facts, there's only talk about what we know for certain," Lavrov told the state-run RIA Novosti news agency. "When we ask for more detailed evidence, they say, 'You know, it's all secret, so we can't show you.' That means that there are no such facts."
Russia, which has major trade deals with Syria, is sending a delegation to Washington for "dialogue" with members of Congress, the Kremlin said Monday. When the two sides share "opinions and arguments, then we'll better understand each other," said Valentina Matviyenko, speaker of the Federation Council, the upper house of parliament. "And I hope that the U.S. Congress will take a balanced position" and reject military intervention.
In the region, meanwhile, Yemen's parliament announced its opposition to any outside intervention in Syria on Monday.